"The amniotic egg enclosed by an eggshell design is employed for reproduction by most terrestrial animals, including many turtles and other reptiles, birds, and prototherian (egg-laying) mammals, (amniotes), in which the embryo develops inside of an amnion.
This design is very different from the anamniotic egg (an-amniotic or non-amniotic) which is not surrounded by an eggshell and contains the embryo of a fish, an amphibian, or a mammal. This egg design is typically much smaller than the amniotic egg and is more dependent on environmental conditions than are shelled eggs.
Anamniotic eggs are enclosed in chorion membranes and lack both
an eggshell and extraembryonic membranes. In contrast, the amniotic egg consists of a set of fetal membranes including the amnion, chorion, and allantois surrounded by an external shell that is either strongly mineralized (as in rigid-shelled eggs) or weakly mineralized (as in parchment-shelled eggs).
The extra-embryonic membranes enclose specific egg elements, store nutrients, collect wastes, and regulate gas and fluid exchange between the egg and the external environment. To this over simplification must be added at least
Anamniotic eggs are enclosed in chorion membranes and lack both
The extra-embryonic membranes enclose specific egg elements, store nutrients, collect wastes, and regulate gas and fluid exchange between the egg and the external environment. To this over simplification must be added at least
---five main classes of egg reproduction that greatly complicate egg evolution: ovuliparity (external fertilization), oviparity (embryos in eggs), ovoviviparity (internal retention of the egg until it hatches), histotrophic viviparity (zygote development within the mother’s oviducts and nutrients are provided by intra-uterine cannibalism), and hemotrophic viviparity (nutrients are provided by the mother via a placenta).
The evolutionary importance of the amniotic egg was because the “amniotic egg with its complex fetal membranes was a key innovation in vertebrate evolution that enabled the great diversification of reptiles, birds and mammals”. Evolution of this design was first required for life to evolve from the marine life of fish to the terrestrial life of reptiles.
*Evolutionists have never been able to document even the most fundamental steps of this required evolution, even admitting that “It is debated whether these fetal membranes evolved in eggs on land as an adaptation to the terrestrial environment or to control antagonistic fetal–maternal interaction in association with extended embryo retention (EER).”
Two models of eggshell evolution exist: “In the terrestrial model,
non-EER oviparity was the primitive condition; oviparity with EER and viviparity evolved multiple times in amniotes. In the EER model, the evolutionarily labile reproductive mode of EER across oviparity to viviparity was primitive, while non-EER oviparity evolved multiple times in amniotes.”
Although the researchers have concluded that the EER model has overturned the once widely accepted Romer model, I fail to see how allowing the embryo to stay in the womb longer to develop further solves the many problems of the evolution-of-the-egg problem. Evolutionists believe that the amniotic egg evolved but do not know where and how, and both existing theories have major problems. What is totally ignored in this, and most, reviews of egg evolution, is the fact that the yolk sac, amnion, the chorion, and allantois are all required as a functional set because the system is irreducibly complex.
The evolutionary importance of the amniotic egg was because the “amniotic egg with its complex fetal membranes was a key innovation in vertebrate evolution that enabled the great diversification of reptiles, birds and mammals”. Evolution of this design was first required for life to evolve from the marine life of fish to the terrestrial life of reptiles.
*Evolutionists have never been able to document even the most fundamental steps of this required evolution, even admitting that “It is debated whether these fetal membranes evolved in eggs on land as an adaptation to the terrestrial environment or to control antagonistic fetal–maternal interaction in association with extended embryo retention (EER).”
Two models of eggshell evolution exist: “In the terrestrial model,
Although the researchers have concluded that the EER model has overturned the once widely accepted Romer model, I fail to see how allowing the embryo to stay in the womb longer to develop further solves the many problems of the evolution-of-the-egg problem. Evolutionists believe that the amniotic egg evolved but do not know where and how, and both existing theories have major problems. What is totally ignored in this, and most, reviews of egg evolution, is the fact that the yolk sac, amnion, the chorion, and allantois are all required as a functional set because the system is irreducibly complex.
*The amniotic egg requires all these functional structures to survive."
CEH